Abstract The transition from water to land is perhaps the most dramatic event in the history of life after the rise of photosynthesis, sexuality and predation. During the late Neoproterozoic and the early Palaeozoic, some green plants, fungi and animals happened to overcome the constraints that linked them to the primeval aquatic environment of life, became progressively adapted to the terrestrial, aerobic environment and finally contributed to its change through time. We do not know how many taxa initially survived this trial, but we have some indication of the result in extant life: a threefold world of pluricellular terrestrial organisms, all depending on each other to various degrees and surrounded by a cryptic world of bacteria and unicellular eukaryotes. Fossils provide us with acceptable information about the evolutionary history of only two of these worlds: embryophytes and bilateralian animals. The molecules of their living representatives can only begin to tell us how they gained the complexity that allowed them to achieve this remarkable adaptation to life on land and in air.